In offices, instruments such as electronic keyboards are commonly accessed from desks. However to minimize operator fatigue and encourage proper posture it is desirable to present the instrument to the operator at a suitably elevated position which is ergonomically efficient.
In some apparatus the keyboard support is not only able to be adjusted in altitude but is also able to be adjusted in attitude (i.e. angle of tilt).
Controls for adjustment of keyboard support elevation (and, if available, tilt) should be accessible and convenient for the operator both in respect of location and ease of operation. Desirably adjustment of altitude and/or tilt could be accomplished with on hand and without risk of damage to long fingernails. The support and adjustment mechanisms should be robust and capable of withstanding overload such as a person sitting or leaning on the support. Quick, positive, secure and convenient locking of the support at a desired height and/or at a desired angle would be advantageous.
It would further be desirable to simplify the manufacture and construction of keyboard support apparatus.
In most apparatus of this kind a threaded bolt and handle are used to clamp the parts at a particular altitude, and if tilt adjustment is provided a separate threaded bolt and handle are provided to clamp the parts at a specific angle of tilt.
U.S. Pat. No. 4,691,888 describes apparatus having a mounting bracket adapted to be secured to a desk, a keyboard support member, linkage bars pivotally mounted to the mounting bracket and to the support member whereby the support member is adapted for movement between a raised or lowered position relative to the mounting bracket and locking means for immobilizing the apparatus against such movement. In described embodiments the locking means is a clamp assembly whereby the linkage bar is clamped to the support member by a threaded bolt extending through the bar and support member and cooperating with a threaded handle.
That apparatus is convenient to use but relies upon the clamping force and friction between the parts for locking and if either is inadequate there is a risk of damage to equipment or injury to the user.
Other apparatus has been proposed in which the locking mechanism involves engagement of a pin with an aperture of the mounting bracket. The pin may be driven by a bowden cable through a link bar into an aperture of the mounting bracket. That arrangement suffers from a difficulty in engagement as well as in difficulty of control. Tolerances required to facilitate locking engagement of the pin and aperture result in an unsteady mechanism.
An object of the present invention is to provide a keyboard support apparatus which avoids at least some of the disadvantages of prior art and/or which meets the desiderata discussed above by more efficient means than prior art.
An object of preferred embodiments of the present invention is provision of a keyboard height adjustment mechanism which is simple, positive in locking, reliable and robust.
A further object of preferred embodiments is provision of a locking means for a keyboard support apparatus which allows selection between (a) a first mode in which tilt adjustment is permitted and altitude adjustment is prevented, (b) a second mode in which altitude adjustment is permitted and tilt adjustment is prevented and (c) a third mode in which both tilt and altitude adjustment are prevented.